As is always the case at this time of year — especially in Maine — I rely more on the behavior of wild birds as an indication of the season rather than on current climate conditions. The first full day of spring brought a few inches of wet, heavy snow and a plunge in temperatures, but I found I could not fall into the pit of disappointment brought on by the weather. Not fully, anyway.

As early as mid-February, I knew my heart could not deny spring. It began with our resident cardinals waking me up around dawn every morning with their singing. I am always amazed, and humbled, at how light and carefree their undulating songs can make me feel.

Contrary to popular belief, both male and female cardinals sing. Mated birds will engage in countersinging, with one member of the pair singing a phrase that is immediately matched by the other. The first singer then will change the phrase and its mate will follow suit, again matching the leader’s song.

Not to be outdone, the mourning doves began their humble, gentle cooing courtship songs. What I was hearing was what ornithologists term the “long coo,” series of five or more drawn-out, mournful-sounding notes. This song is specifically sung by the male who is still looking for a mate. Later, once he has found his mate, he will sing the “short coo,” a brief, two- or three-note song, often from a nest or potential nest site.

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I was surprised to hear a song sparrow’s energetic voice joining the cardinals and doves in the morning chorus. I knew song sparrows migrated, and, having lived farther north and inland in Maine, I was accustomed to their return in March or April. A recheck of a distribution map showed a small strip of coastline where these birds could be expected to remain year-round.

One day — shortly before the first-day-of-spring snow — I heard the cheerful whistles of the black-capped chickadee’s “fee-bee” song. This can be a loud, strident song given primarily during territorial skirmishes, or a softer vocalization uttered during mate-feeding. While the territorial version can be sung at any time of the year, I always seem to hear it more often in spring.

And today — despite temperatures hardly getting out of the 30s — I saw examples of courtship rituals in a small group of red-breasted mergansers. This is a very interesting time of year, as we begin to see the breakup of winter flocks of visiting migratory birds and their transition to courtship behaviors before departure for their summer breeding grounds.

I observed a peculiar bobbing behavior of the male mergansers as they competed for the attention of the few females in the group. First, the male straightened his neck and pointed his bill skyward, then abruptly pulled his neck down toward the water while keeping his bill pointed up. This caused his hind end to tip up out of the water. Later, looking at an illustration of this maneuver, it showed his body folding into a V posture with the base of his neck the lowest point, below the surface of the water.

Ornithologists have called this elaborate behavior a “salute-curtsy.” Although whimsical in nature, the term is certainly accurate — it definitely looked as if the bird was first saluting, then curtsying.

As exciting as all these behavior changes are, nothing beats the arrival of migrants. Common grackles, turkey vultures and red-winged blackbirds, and robins covering every square foot of close-cropped, bare lawn, it seems — the onrushing life heralds the spring season.